ZYX vs. MCPx FBL behavior q's

[nbisme]

I tried searching, but couldn't find a great answer. Keep in mind I'm a noob, so feel free to school me.
https://www.helifreak.com/showthread.php?t=415860
This thread talks about the INHERENT DIFFERENCE between the zyx (and it's siblings) vs. the mcpx 3-in-1 (beastx, and some others).

Imagine a drifting heli, and the pilot corrects for it....

the zyx has the swash always COMES BACK TO CENTER after making the correction requested by either the pilot or by the stabilizing control loop, whereas the mcpx/beastx swash will STAY TILTED to maintain hover until it notices another input either from the pilot or the gyros.

The end result is that a perfectly mechanically level swash on a zyx will drift sideways due to translating tendency. Note, this is not a roll/pitch/yaw movement. It is a level sideways drift at constant altitude.

My question: SHOULD the zyx pick this movement up and correct for it., thereby going into a constant back and forth between leveling swash-correcting-leveling swash-correcting-etc.? (my experience with the zyx tells me it doesn't, and it's my job to constantly give slight right cyclic to compensate for tail rotor thrust in a hover)

I know the answer is that I shouldn't care because heli's aren't meant to hands-off hover anyways, and I should always be flying it. I KNOW THAT, but I'm still curious of the theory behind the zyx and how it's different from other controllers.

[Crashtestheli]

I can not answer your question, but I think I can help

The xyz with the beginner settings on a 450 pro flys like my mcxp. Very very close.

The xyz on the mild 3d in very hard to hover

[Drivinfast247]

The mCPx uses A3X flybarless, not BeastX.

[nbisme]

Originally Posted by Drivinfast247

The mCPx uses A3X flybarless, not BeastX.

Of course...but they behave similar right? If you put a heli with beastx on the bench and give a right aileron input, what does the swash do? Does it ever come back to center without the heli moving? The mcpx's swash would never come back to center. The zyx would after a second or so.

[Dr. M]

Bench behavior is no indication of what the gyro will do in the air.

FWIW, neither the BX, nor the mcpx, nor most other FBL controller will correct for translating tendency in a hover. Only those systems featuring auto-level routines (sk720) will do this. You need an accelerometer to sense this sideways drift.

[RedOctobyr]

Originally Posted by Dr. M

Bench behavior is no indication of what the gyro will do in the air.

Maybe to an extent. But I agree with nbisme's point.

My mCP X could have a swashplate that's tilted 10 deg forward with the sticks neutral (ie- swash very much not level). But if I just lift off using only collective, it will feel the forward tilt as I come off the ground, and it will tilt the swashplate back. It may not bring it into a perfect hover, but you could say it goes by what it senses, not by the neutral positions of the servos, once in the air.

Once I bring the tilted-swash mCP X into a hover, it will keep it there just as well as if the swash was perfectly-leveled on the ground. And if you give it throttle while on the ground (to activate the FBL), then give some cyclic, the swash will tilt, and remain there indefinitely until the gyros sense the change you asked for.

If you adjust the swashplate on your ZYX heli so it's at the same 10 degrees forward, and take off, I expect it will take care of the gross problems (the 10 deg forward tilt), and will hopefully avoid just slamming you forward into the dirt. But you'll keep drifting forward, even after you correct and bring it back to a hover. It wants to keep leveling the servos to neutral, rather than *just* "listening" to what the gyros are telling it.

Likewise, on the bench, the ZYX will tilt the swash based on your cyclic input, but then it will put the servos back to neutral, rather than staying tilted until it feels the change you commanded.

The differences in behavior between the two systems, are, in my opinion, very "consistent" between their on-the-ground behavior, and what they do in the air.

And I would prefer that the ZYX correct for a swash that's not perfectly level. It and the mCP X are the only FBL systems I've used, so I don't know how other systems (like BeastX, 3GX, and others that don't have accelerometers) behave. I don't know which behavior is "normal".

[Dr. M]

I agree that the ZYX will drift if the swash isn't level. However, by looking at the flight behavior of this FBL controller, I do believe (though not tested) that it will correct for a grossly unlevel swash provided you can actually take off in that state... though you'd have a very poorly flying machine.

IMO, the ZYX control algorithm is smarter than the mCPX. Think of it this way: there is no flight scenario for which you'd ever want your swashplate to remain tilted (i.e. not return to center) after a cyclic control is released. Lest you enjoy mopping up your bird after a flip-over during spool-up.

[FreshMeat]

I have noticed on my mcpx that the main shaft is tilted ever so slightly to the right I am guessing this is to counteract the push from the tail? if so would it be safe to assume that with 450 plus sized cp helis you need to give a slight right aileron input to maintain hover even if you have a fbl system? I have seen youtube clips of trex 450's with helicommand doing hands off hovers with just the tiniest amounts of drift, would be a nice function if one day you could just hit a switch and bring the heli back to starting position then continue learning the tail in hover again, if it starts to get away flick the switch again to save it and bring it back to starting position again, maybe with a gps function some way or another

[InFocus]

With even my low cost copter-x FBL, hover is hands off, and only slides based on the direction of the wind. BeastX I bet is the same way.

As to the 'come back home' switch, this already exists too. Look up DJI wookong system.
It isn't cheap..

[LawnDartHeli]

I like the fact that the zyx/Cx units return to center on the swash...I don't want may 450 doin the blade scrap chicken dance on spool up just because I bumped the cyclic. Mine hovers fairly hands off anyways though.

sent from my phone using circus midgets

[nbisme]

Someone correct my logic if I'm wrong:
1) We agree a well setup RC heli has a perfectly level swash throughout its travel range
2) We agree the zyx always goes back to center without pilot/tx input
3) We agree that our RC helis exhibit translating tendency
4) We agree that the zyx does not/should not correct for translating tendency (no accelerometer)

Therefore: a properly setup RC heli with zyx should not hands off hover. It should hands off have a slight right to left level-altitude drift due to tail rotor thrust (no leaning, just drifting).

Thanks for the input so far.

[LawnDartHeli]

Sounds pretty solid.

sent from my phone using circus midgets